Compose and YUV fragment processor clone implementations

Change-Id: If4d9f1aaf0e5939afb5ad5825d7198db18541926
Reviewed-on: https://skia-review.googlesource.com/27060
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
2 files changed